1. Field of the Invention
The invention relates to a method, at a draw frame for fibre slivers, of adjusting the nip line spacing of a drawing mechanism, which has at least two drawing mechanism roller combinations, of which at least one is so mounted that it can be adjusted, wherein each drawing mechanism roller combination consists of at least one driven lower roller and at least one upper roller (press roller) lying on top of the lower roller and so mounted that it can be lifted off, and encompasses an apparatus for carrying out the method.
2. Description of Related Art
In practice, adjustment of the nip line spacings carried out without fibre slivers in the drawing mechanism, that is to say the fibre slivers are drawn off from the drawing mechanism completely and, subsequently, the nip line spacings are adjusted. It is not possible, by that means, to optimise existing drawing mechanism settings whilst using the same fibre material.
In a known appartus (DE-OS 20 44 996), the mountings of the intake and middle lower rollers are displaceable on the frame of the machine so that the extent of the drawing zone can be matched to the particular fibre staple. A tensioning pulley wheel, which is displaceable in a guideway in the frame of the machine, allows the length of the toothed belt to be modified in accordance with the changed spacing between the axes of the middle roller and a guide pulley wheel, brought about by displacement of the intake roller. The middle roller is driven by a further toothed belt. The latter toothed belt is tensioned by a tensioning pulley wheel which is fastened to the machine frame and which can pivot about one axis; as a result, it can also be matched to changed spacings between the axes of the intake roller and middle roller. It is disadvantageous that displacing devices for displacement of the intake roller and the middle roller and additional tensioning devices for re-tensioning of the toothed belts after the displacement operations are necessary, requiring a considerable outlay in terms of construction. In addition, it is disadvant-ageous that a number of work steps are required for the displacement operations and the subsequent re-tensioning operations. The belt tension is destroyed by the displacement process. Where the displacement is carried out manually, spacers are inserted between the mountings, the mountings being pushed against the spacers so that, in this case too, the amount of set-up work is considerable. Finally, the displacement and re-tensioning operations result in a doubling of potential error sources when setting the spacings and belt tensions.